Saturday, December 4, 2010

Eastern Washington Gloom

8 PM Update...the Huskies DID win and will be going to a bowl game!

You think of eastern Washington and what are the first thoughts that come into your head? Dry--no doubt. Sunny and warm? Well for the warmer half of the year this is true...but eastern Washington has its dark side...the tendency for low clouds and fog to collect there from November into February.

The last few days have been good examples. Below are two satellite images from yesterday (Friday, Dec 3). The first from the usual NWS operational satellite and second from the high-resolution MODIS satellite.

Eastern Washington is full of low clouds and fog...and you can see a line of low clouds in the Willamette Valley (also a foggy place), the Chehalis Valley and portions of the Puget Sound basin. In the latter the fog tends to burn off to a much greater degree than eastern Washington.

Foggy conditions tend to occur when high pressure is over our region--bringing light winds and relatively cloud-free conditions aloft. In such situations the earth can effectively radiate heat to space, cooling the surface down to the dewpoint...thus the clouds and fog. Mixing from wind helps to dissipate the low clouds...and this is where eastern WA has a big problem...it is in a topographic bowl. Here's the proof from a google topographic map:

Eastern Wa is surrounded by the Cascades to the west, the Okanogan Highlands to the north, the Rockies to the east, and the Blue Mts to the southeast, with higher terrain north of the Columbia River finishing the enclosure. So on these cold, high- pressure days the cold air collects and deepens in the basin, with a stable inversion capping the cool layer. The clouds are good at emitting infrared to space and maintaining themselves. The result--one gloomy situation.

In Spokane, the number of overcast days per month for November, December, January are 17, 21, and 10, with the corresponding number of heavy fog days (1/4 mile visibility or less) being 8.5, 11.7 and 9.3. You will need vitamin D there for sure.

But wait! There is something else--freezing fog. Since there is often subfreezing temps while this fog is around, the roads are often glazed by dangerous freezing fog. In fact, the National Weather Service has had a freezing fog warning out for several days now.

Fortunately, there appears to be a break in the fog over Pullman for the Apple Cup game...an intervention by higher powers that is a sure sign that the UW Huskies will win. However, if my ability to forecast the weather is admittedly uncertain and my bias in this matter self-evident, I suspect my skill in predicting football scores may be questionable.

14 comments:

wavelength said...

go cougs

Sail on MIke said...

Does the MODIS satellite pass over this area on a regular basis? The image is beautiful.

Don said...

GO COUGS!!

Rivrdog said...

Your Dawgs won, as they do in most Cougar-large Dawg encounters...

Thom said...

Drove across the state today, it felt like driving through a black & white photograph. All the pine trees west of Thorp to Indian John are heavily coated with ice from the fog yesterday, quite an amazing sight with a low sun going down over the cascades.

Katie said...

Living in SE Washington, I can attest to the fact that it is very gloomy, and that we have this problem every winter. We need a good storm to come blow it all out.

Bonnie said...

It hasn't been above freezing for 2 weeks here in Eburg. Although today looks promising ... according to our Davis Vantage Pro 2 weather station, it is currently -1C ... so close!

Kevin Purcell said...

Sail on MIke said: "Does the MODIS satellite pass over this area on a regular basis? The image is beautiful."

MODIS is the imager that flies on the Terra and Aqua satellites.

Terra and Aqua share the same sun synchronous orbit but about 12 hours out of phase with each other.

Each satellite makes a (sun synchronous ... so the sun angle is the same for each pass) pass over every point on the earth once a day (well twice a day but one pass is at night so it's not used for imagery).

Terra makes a N to S pass (descending) at around 10:30am at the equator.

Aqua makes a S to N pass (ascending) at around 1:30pm at the equator.

You can find images at the MODIS Image a Day site http://modis.gsfc.nasa.gov/gallery/showall.php

You can also look up recent images for any location on the planet at http://modis.gsfc.nasa.gov/data/

Kenna Wickman said...

Interesting collection of comma clouds off in the Pacific this morning in the visible satellite. It looks like California could get hammered.

smokejumper said...

I went to the Apple Cup and drove home this evening (Sunday), and it was a nice drive from Pullman. Snow cover the whole way (Not deep), rolling hills of the Palouse make for great snow drifts!

Anyway, driving back west, the contrast of a brillant white surface and some really dark clouds w/ a heavy sleet shower, the sky was purple! So wish I had a camera, dunno if the ice fall played a role in it.

A said...

As a UW grad who lived/worked in Seattle and purposely retired to Klickitat county near the Columbia Gorge, I bet I can see Mount Rainier more days from here than you can in Seattle. The winters may have fog and snow but there are few people, pleasant summers, and good views.

bob said...

Sail on Mike, yes Modis imagery is public, bit I think that saying it is available is a bit of a stretch. In my experience, it is a slow and difficult job to find the information you want on any federal web site, NASA included. I suspect that Cliff has a library of links to the images he publishes. Cliff, any chance that you can share some of your favorite gov imagery links? The curious of us would really appreciate it!

Bob said...

A sad commentary: I find it a bit sad to study the "Pageviews Last Month" plot on this blog. A few of us seem to visit here regularly. Then, when it looks like we might be playing bumper cars, we see the enormous number of folks who are aware of this blog, but don't visit until disaster looms. I wonder what kind of world we would have if more people wanted to know more about her in an ongoing way. Why are the curious so few?

Kevin Purcell said...

Bob:

If you don't want to mess with the granules as HDF files (hey, its fun!).

Use the MODIS rapidfire subsets page. RGB images in formats you can use.

Saturn Island is pretty good for WWA

http://rapidfire.sci.gsfc.nasa.gov/subsets/?subset=AERONET_Saturn_Island

Use the change vector options to add coasts + borders to orientate yourself on a cloudy view.

I suspect this the one Cliff uses. There are others for the whole planet.

http://rapidfire.sci.gsfc.nasa.gov/subsets

Read the FAQ to find out more (e.g. using the realtime granules and finding out when the sats are overhead)

http://rapidfire.sci.gsfc.nasa.gov/faq/